1. Field of the Invention
This invention relates generally to inflatable type modular occupant restraint systems for passenger vehicles or, as it is more commonly known, an air bag restraint system. Such a system may be installed in an automobile or other vehicle, at least in part on the steering wheel for the protection of the driver and also in the dashboard or passenger side instrument panel for passenger protection in the event of a collision. More particularly, this invention relates to an improvement in the means for guiding and directing the initial deployment of the cushion along a predetermined path.
2. Description of Prior Art
An air bag restraint system typically includes a canister, which has an open side and encloses an inflator and at least part of an air bag, and a cover which conceals the module from view. When the air bag module is designed for the passenger side of a vehicle, the container may be located just behind the vehicle dashboard, cosmetic cover, or passenger side instrument panel (hereinafter referred to as "dashboard") and the cover may form an integral part of the vehicle dashboard. Alternatively, due to structural and cosmetic considerations, a passenger side air bag may be mounted such that the edge of the container opening may be a couple of inches behind the dashboard.
When the vehicle is involved in a collision, a crash signal initiates operation of the inflator to cause the air bag to deploy. The inflator produces an inert gas (e.g., nitrogen) which is directed under pressure into the air bag to force the air bag out of the container incorporated in the module and into the passenger compartment of the vehicle. As the air bag is forced out of the container, the pressure exerted on the dashboard causes selected portions of the dashboard to separate, in a predetermined manner along tear seams or break away seams (hereinafter referred to as "tear seams") to enable the air bag to be directed into the passenger compartment. As the air bag is directed into the passenger compartment, it is inflated by the continued flow of gas produced by the inflator. Care should be taken so that the air bag is not torn or punctured during deployment by sharp edges of the ruptured seams of the dashboard or on structural supports behind the dashboard.
During deployment of a passenger side air bag mounted some distance behind the instrument panel or dashboard the air bag expands until sufficient pressure develops to break the tear seams of the dashboard. Should sufficient pressure fail to develop or should the air bag find a path of lesser resistance the air bag may not deploy properly. Should the air bag find a path of lesser resistance behind the dashboard the bag may continue to expand in the direction of lesser resistance inflating completely behind the dashboard thus making the air bag unavailable to protect the vehicle occupant. Alternatively, the air bag may continue to inflate until another opening is found, for example at the bottom of the dashboard thereby allowing the air bag to expand down to the floor of the passenger compartment. This mode of deployment would provide inadequate protection for the vehicle occupant's torso and upper body. Also, the air bag may continue to inflate and expand behind the dashboard extruding itself behind the dashboard until the dashboard fails at other than predetermined failure points. At this time the bag can expand toward the occupant transporting the dashboard into the occupant thereby causing injury to the occupant. Such improper deployment of the passenger side air bag would render the air bag unusable for the protection of the occupant and may result in further injury to the occupant.
Also, of concern is that during manufacture, shipping, and storage, extraneous material such as small pieces of metal, nuts, bolts, fasteners or the like may fall into the canister. Storage herein is taken to mean storage of the module in a warehouse or the like prior to installation in a vehicle and storage behind the dashboard of a vehicle prior to deployment in the event of a collision with another object. The release of this extraneous material during deployment of the air bag may result in injury to the vehicle occupants.
Solutions have been suggested to guide the deployment of an air bag for driver protection. Cok et al., U.S. Pat. No. 4,903,986 and Miller et al., U.S. Pat. No. 5,013,064 provide such a system comprising a container and cover which permit initial deployment of the cushion along alternate paths parallel to the driver should the cushion be prevented from deployment along its normal intended path toward the driver.